Each of the examples listed has a different symbolism in the story; for example, Old Man Warner represents the continuing success of the town as the ritual is performed, while Tessie represents the newer thinking about the cruelty and needless nature of the ritual in modern times.

One good thesis statement could focus on how each symbol affects the context of the story as it progresses; the black box is innocent as it is introduced, and only gains its true purpose when the full ritual is revealed. You could write: "Each symbol gains a second meaning at the story's end." To expand on this, you could explain the first meaning of the symbols, and then the second meaning gained by the full reveal.

Another good thesis could focus on the relationship of the symbols to each other; the stones are meaningless until the end, but are comparable to the box with its slips of paper. You could write: "The symbolic meaning of each object is magnified when analyzed together." A discussion of the purpose and relevance of the symbols could then lead to an examination of how they work together to form one larger symbol.